Liberal Arts, Josh Radnor, 97 mins, 12A

You don't need a degree to enjoy this bookish Allen-style New York romcom, but it would help

Elizabeth Olsen and Josh Radnor take a break from studying

American campus comedy Liberal Arts is utterly charming. And indeed, I was utterly charmed – but it was only after watching it that I began to wonder whether it was quite as delightful a deal as I'd thought. Enjoyable, though, the film certainly is. This is a walking-and-talking movie, an urbane, leisurely piece about, and so partly for, bookish types – very much a rarity in United States cinema, or any other corner of world cinema outside a few square miles of Paris.

It's the second feature by writer-director-actor Josh Radnor, whom you might recognise from the sitcom How I Met Your Mother. He's personable company as Jesse, an academic in his thirties who's living in New York, beginning to get jaded, and newly split from his girlfriend. Just in time to pull him out of his slough is an invitation from his old professor, Peter Hoberg, to revisit his leafy alma mater.

Peter, reluctantly about to retire, is a 1960s idealist who taught Jesse everything he knows – except disillusion, which he's learning for himself. He's played by Richard Jenkins, recently the mob's liaisons exec in Killing Them Softly. Here, Jenkins merges his trademark dryness with a laconic affability, and he's one of the richer grown-up pleasures that the film affords.

Through Peter, Jesse encounters a female undergraduate who's into improvised theatre and, aged 19, is full of untainted enthusiasm. Her name is Elizabeth, but everyone calls her Zibby. Did you catch me wince as I wrote that?

Zibby is played by Elizabeth Olsen, which is why I winced slightly less than I might have done. Olsen is magnetic on screen, sensitive and smart; recently, she was scarily detached as the cult captive in Martha Marcy May Marlene. Zibby captivates Jesse because she's brimming with joie de vivre – yet she isn't one of those recklessly whimsical romcom creatures who are now generically known as "Manic Pixie Dream Girls" (the term, coined by US critic Nathan Rabin, is embodied by Zooey Deschanel in practically anything). More of a Pensive Zen Gamine, Zibby is thoughtful and articulate and, of course, Jesse falls for her. (The film's real Manic Pixie is male, a blissed-out tree-whisperer played by Zac Efron, and it's a mark of Efron's very decent acting that you only slightly want to slap him.)

The spell is sealed by Zibby's giving Jesse a classical-music mix CD, and the film's cutest – certainly most Woody Allen-ish – conceit has Jesse drifting beatifically round Manhattan while passersby smile sexily at him, his world transformed by Mozart and Massenet.

Then Zibby coyly writes to Jesse that she'd like him to be her "gentleman caller". He has misgivings – he's 16 years older, and we see him cringe as he works out the sums. Still, he goes to visit her, and that's when the impediments to the marriage of true minds start piling up. One impediment is his horror at realising that this finely discerning creature likes to read vampire romances (the paperback title we see is – like it! - Lunar Moon).

After that, the film shifts towards a more delicate register of moral comedy, and ends up making Jesse look excruciatingly scrupulous and gallant when realising the full extent of Zibby's old-fashionedness. This all seems designed at once to make her a more unthreatening love object, and him preternaturally sensitive and noble (which doesn't mean he isn't also a confused dork). But there's a very conservative male fantasy at work here, making Zibby that bit less real.

Explicit reference is made to William Blake's Songs of Innocence and Experience – and on the experience side is Judith Fairfield, the high-toned professor who once inspired Jesse with a love of the Romantics. Now, frosty and suavely castrating, she represents disillusionment at its harshest. It's a role that the ineffable Allison Janney makes the most of, and imbues with the very crispest chilled-Martini amusement. But it's still a caricature: not to put too fine a point on it, the embittered old maid who should never have wasted her life on literary loves.

So, a film ostensibly about the passion for literature turns out to be cautiously anti-learning. The most hapless character is a student (John Magaro) who feels "aggressively unhappy" – apparently because he's been reading too much David Foster Wallace. The film's epigraph is from Ecclesiastes – "He that increaseth knowledge, increaseth sorrow" – and you can imagine how Eric Rohmer would have made an ironic tease of this opening proposition. Here, however, it's easy to read the words as backing up the message that plain commonsensical wisdom beats book-learning hands down.

It's irksome to detect this reactionary streak in what's otherwise a literate, neatly formed comedy of manners. These days, you have to applaud any American film that makes room for sensitivity and smart talk: Liberal Arts will be as cherished among Eng Lit students as Before Sunrise was among backpackers. But it's a little too pleased with its own likeability – and so, finally, is Josh Radnor the actor.

You may balk at falling quite as hopelessly for Olsen's Zibby as the film wants us to: Radnor (or at least cameraman Seamus Tierney's lens) is seriously smitten with those huge manga-heroine eyes, and can't resist lighting her a deep radiant gold. But Radnor is astute enough to mix some tart urbanity in with the fuzziness. I recommend Liberal Arts, with caveats. I'd be surprised if you didn't enjoy it a lot. But then you'll wonder whether it's quite as liberal as it makes out.

Critic's choice

The 56th BFI London Film Festival kicks off on Wednesday with Tim Burton's Frankenweenie, with its very first competition line-up including Ozon, Audiard, Winterbottom and Martin McDonagh's Seven Psychopaths (10 to 21 Oct; bfi.org.uk/lff). Christian Petzold's taut drama Barbara features the mesmerising Nina Hoss as a woman on the edge in the old East Germany.